Three-Axis Magnetic Field Mapper for a Neutron Electric Dipole Moment Experiment at Los Alamos National Lab 

Measurement of a neutron electric dipole moment (nEDM) through a Ramsey separated oscillatory fields (SOF) method requires a magnetic environment of sufficient uniformity to reach the desired experimental accuracy. With the nEDM experiment at Los Alamos National Lab (LANL) aiming for an EDM measurement sensitivity of d ~ 10^-27 e cm, it is crucial that magnetic field gradients within the experimental area be minimized. Therefore, in addition to magnetic shielding and magnetometry methods, it is important that the ambient magnetic field be thoroughly understood. For this purpose, the LANL collaboration has designed and assembled a robotic mapper that can measure the field within a cylindrical volume inside the magnetically shielded room (MSR). The implementation of such a device provides a unique challenge in that many of its components must be non-magnetic and free of magnetic impurities that could interfere with fluxgate magnetometer measurements. The mapper will provide accurate measurements of the field present in the experiment and gauge the effectiveness of the multiple magnetic shielding methods in place around the experimental area, as well as measure the stability and uniformity of an applied B0 holding field necessary for the SOF method. The process and results of the mapper’s implementation will be presented.